Detailed Explanation of High-Quality and High-Yield Cultivation Techniques for Pak Choi

Pak choi, also known as non-heading Chinese cabbage, bok choy, or green vegetable, is relatively commonly cultivated in the south. The aboveground leaves are used for consumption; the quality is fresh and tender, and it contains relatively high amounts of carbohydrates, vitamins and some minerals. It is suitable for both fresh eating and drying, and is one of the vegetables widely enjoyed by the general public.
1. Cultivation season and cropping system: According to climatic conditions, through variety selection, staggered sowing dates, plus reasonable fertilizer and water management measures, pak choi can be produced year-round to supply the market. Generally, based on maturity period, bolting period and suitable cultivation season, it is divided into three types: autumn-winter pak choi, spring pak choi and summer pak choi. When cultivating, the first considerations should be the developmental characteristics, adaptability and disease resistance of the variety. For winter-spring cultivation, spring pak choi varieties with strong winter hardiness and late bolting can be selected. In the Lingnan region there is no severe cold in winter, and pak choi can grow vigorously throughout the entire winter. In spring, autumn-winter pak choi varieties with weak winter hardiness can be selected for cultivation as "vegetable seedlings." In the high-temperature and rainy summer season, varieties with multiple resistances and broad adaptability should be selected. For autumn-winter cultivation, autumn-winter pak choi varieties should be selected, and generally seedling raising and transplanting are carried out. In South China, sowing generally starts from September to December, with supply in batches and stages until February of the following year. Generally, harvest can be done 20-40 days after field planting.
For spring cultivation of pak choi, the main purpose is to harvest young tender plants for consumption, sowing from February to April and harvesting from April to May. In summer, the main focus is on cultivating pak choi "vegetable seedlings," starting sowing in early May and continuing until August. After sowing, young tender plants are successively harvested for market in 25-30 days. Among these, those sown from late July to early August can, in addition to a batch of "vegetable seedlings" being marketed, also have thinned seedlings transplanted to the field for early autumn pak choi cultivation.
Cropping systems include crop rotation, intercropping, mixed cropping and relay intercropping. In areas with severe disease and pest problems, crop rotation should be adopted, and generally rotation can be carried out with cucurbits, legumes, root vegetables and field crops. If continuous cropping is necessary, organic fertilizer must be applied in increased amounts, attention must be paid to early plowing and sun-bleaching, and management must be strengthened. Common intercropping, mixed cropping and relay intercropping include: spring vegetable seedlings or spring-grown large vegetables intercropped or relay intercropped with solanaceous fruits, legumes and cucurbits; winter intercropping with spring cabbage, lettuce, etc.
2. Sowing and seedling raising: Pak choi grows relatively quickly in spring and summer and the plants are small, making transplanting difficult, so direct seeding is mostly used. For seedling raising and transplanting, the seedling methods include heat-resistant seedling raising and cold-resistant seedling raising.
Heat-resistant seedling raising focuses on use during the hot weather from April to August. Select heat-resistant or heat-tolerant varieties, and choose sandy loam or loam as the seedling site. The soil must both retain water and fertilizer and be loose and breathable, and fully decomposed organic manure should be applied as base fertilizer to improve the soil physical properties of the seedbed. In addition, appropriately sow thinly for seedling raising; during the seedling stage, the frame can be raised or shade nets can be used to prevent rain and lower temperature, and watering should be strengthened. Timely prevention and control of diseases and pests.
Cold-resistant seedling raising focuses on use during the cold weather from January to March. Select varieties with strong winter hardiness and cold tolerance, and increase seedbed temperature by applying semi-decomposed pig and cattle manure, garbage, etc. Grasp the transition from the end of a cold spell to the beginning of warmth, sow at the right time, sow appropriately thinly, and set up insulated film tunnels during the seedling stage.
Pak choi sown at the proper time can emerge in 2-3 days. After emergence, thinning should be done in time to prevent excessive elongation. Water and fertilizer management during the seedling stage should be flexibly controlled according to soil, seedlings and weather, and attention should be paid to light and frequent watering. Attention should be paid to weed control and disease and pest control during the seedling stage, especially doing a good job of controlling aphids to prevent viral disease.
3. Land preparation, fertilization and field planting: Choose fields with good drainage. For old vegetable plots, thoroughly clean away the residual branches and fallen leaves of the previous crop, and plow and sun-bleach the soil. Apply 1500-2000 kg of pig and cattle manure per mu as base fertilizer, and mix it evenly with the soil after application. The planting distance depends on the variety, season or cultivation purpose. For those grown specifically to harvest young tender plants for food or planted in off-seasons, dense planting is suitable. For autumn-winter cultivation, field planting can be appropriately thinner. Generally, beds 1.5-2.0 m wide including ditches are used, with plant spacing of 15-20 cm. Planting depth depends on climate and soil quality. In early autumn, shallow planting is suitable to prevent heart rot from deep planting; after Cold Dew, deep planting is suitable to prevent cold, and if the soil is relatively loose, planting can be slightly deeper; for clay soil, shallow planting is suitable. Generally, it is suitable for the soil to reach the base of the petiole of the first true leaf. When field planting, select seedlings in the seedbed and dig and plant them successively according to size. Before lifting seedlings, water the seedbed first, which can reduce root damage.
4. Field management: The root system of pak choi is shallow and grows in the surface soil. Although its recovery ability is strong, its absorption ability is weak, and its requirements for water and fertilizer are very strict. Its growth period is relatively short. If fertilizer and water are insufficient, yield and quality are directly affected. During the growth period, sufficient fertilizer and water should be supplied continuously. Under conditions of sufficient base fertilizer, topdressing begins after field planting and reviving, mostly with quick-acting nitrogen fertilizer; urea or 15% urine water can be used, applied once about every week, with concentration gradually increasing, until 10 days before harvest. In humid and stuffy weather, topdressing should not be excessive, otherwise diseases may be induced; in cool weather, pak choi grows quickly, so more fertilizer can be applied.
Water management is generally combined with topdressing. Within a few days after field planting, water cannot be lacking, and especially in summer cultivation, watering should be paid even more attention. During the growth period, the soil should be kept moist frequently. In spring and summer there is more rain, so drainage is the main measure; in hot and autumn-winter seasons, when the weather is dry, watering should be done every morning and evening.
For summer pak choi cultivation, direct seeding is mostly used, and fertilizer and water management are especially important; high temperature and heavy rain can easily cause seedling death, and there are also relatively many diseases and pests. In production, pest control and disease control should be done well, along with measures against high temperature and heavy rain. The main measures are selecting varieties with strong heat tolerance, strengthening seedling-stage management, carrying out rotation, intercropping and relay intercropping, and timely watering.
5. Disease and pest control: The main disease of pak choi is viral disease. If the weather is dry, it occurs more. The main control measures are: pay attention to crop rotation, carry out soil disinfection, use pesticides early to control aphids and remove diseased plants. In addition, there are also white spot disease, sclerotinia disease, black spot disease, etc., which can be controlled with fungicides such as thiophanate-methyl and carbendazim. Pests mainly include striped flea beetles, cabbage caterpillars, diamondback moths, cabbage webworms, etc., which can be sprayed and killed with cartap, fenvalerate, trichlorfon, insect virus No. 2, dichlorvos, etc.
6. Harvest: The harvest period of pak choi depends on weather conditions, variety characteristics and consumer requirements. For spring and summer pak choi in South China, it generally takes 40-50 days from sowing to harvest, with a yield of 1000-1500 kg per mu. For autumn-winter pak choi, it takes 60-70 days from sowing to harvest, and the yield can reach more than 3000 kg. Harvest standard for pak choi: when the color of the outer leaves begins to fade, the outer leaves at the base turn yellow, the leaf cluster shifts from vigorous growth to closed growth, and the heart leaves extend to the level of the bed opening, the plant has fully grown and the yield is highest.